My Home Ideas

Special Offers

Be the first to know about This Old House contests, sweepstakes, and events and receive special offers and promotions from your favorite home improvement brands. We'll even send you regular reminders to enter our sweepstakes.

If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

fan booster

I would like to know how to connect a duct fan booster to the heaters blower motor.However I don't know which wires are the right ones,It seams black and white could be other than black and white.Looks like spaghetti to me.

Re: fan booster

You'll need a multimeter (voltmeter) that can measure 120V, (assuming the boost fan is 120v) available at Harbor Freight or Wal-Mart for $6-$10; the Wal-Mart one comes in a yellow case.

Wait until the heating system is running & attach the black ground wire of the meter to any metal part of the furnace, & touch the other wire to the different furnace wires until you get 120V reading on the meter.

Re: fan booster

Re: fan booster

No need to worry about relays---the 120v furnace blower motor is wired AFTER the relays.

With the voltmeter connected to the right point during a normal heating cycle, it should read 120v when the blower motor comes on, and zero volts when the blower motor goes off; there should be a steel or plastic electrical junction box (similar to a standard electrical wall junction box) somewhere on the furnace that contains these wires & offers easy tie-in for the duct fan wiring.

There should be some written instructions that come with the duct fan, if not you can probably find some on the internet:

Some caveats: many techs feel booster fans in many cases are not necessary because the problem of low air flow can be solved by adjusting the various duct dampers, patching up any leaking ducting with duct tape, etc., & some furnaces have higher speed adjustments on their motor, short runs of flex duct can be replaced with rigid duct for an improvement, etc.

Try all these first; booster fans tend to be noisy in some cases & burn added electricity.

Re: fan booster

Thanks for replying I did what you said and hooked it up.I was talking to someone and they said what you did about air flow,it sounds like the hvac guy didn't put enough air return in.I'm going to try to solve this problem next.Thanks again for your time and have a MERRY CHRISTMAS